1. Related Technical Fields
Related technical fields include route guidance systems, methods, and programs.
2. Description of the Related Art
A navigation apparatus mounted on a vehicle detects a current position of the vehicle by GPS (global positioning system), reads out map data from a data storing section, displays a map screen on a display section, and displays the vehicle position indicating the current position of the vehicle on a map of the area surrounding the vehicle. Therefore, a driver of the vehicle may drive the vehicle using the vehicle position displayed on the map as an aid.
When the driver inputs a destination and sets a route search condition, a route from the current position as a starting point to the destination is searched on the basis of the search condition. The searched route is displayed together with the vehicle position on the map, and the driver is provided guidance along the searched route. Therefore, the driver may drive the vehicle following the searched route.
According to the route guidance, for example, when the driver needs to make a right or left turn at a predetermined turn intersection, audio guidance is output before the vehicle arrives at the turn intersection. To output the audio guidance, one or more route guidance points are set between the vehicle and the turn intersection on the searched route. The route guidance points are more than a predetermined distance away from each other. When the vehicle arrives at each of the route guidance points, a preset audio guidance for each route guidance point is output. See, for example, Japanese Unexamined Patent Application Publication No. H6-295399.
FIG. 2 is a diagram showing route guidance provided by a conventional navigation apparatus. FIG. 3 is a diagram showing a first example of possible route guidance provided by a conventional navigation apparatus. FIG. 4 is a second example of possible route guidance provided by a conventional navigation apparatus.
In FIGS. 2-4, “pr” denotes a vehicle position, “ri” (i=1, 2, . . . ) denotes a road, “crj” (j=1, 2, . . . ) denotes an intersection at which two or more predetermined roads intersect, and “sgk” (k=1, 2, . . . ) denotes a traffic light. Further, “Rt” denotes a searched route, and “h1” denotes a route guidance point set on the searched route Rt.
For example, when audio guidance such as “Please turn left at the second intersection with a traffic light,” is output at the route guidance point h1, it is difficult for the driver to determine which intersection is “the second intersection with a traffic light”. That is, in the case of counting only intersections cr2 and cr3 which have traffic lights sg1 and sg2, “the second intersection with a traffic light” means the intersection cr3, so that the searched route Rt may be the route as shown in FIG. 3. However, in the case of counting the intersections cr2 and cr3 which have the traffic lights sg1 and sg2 as well as an intersection cr1 without a traffic light, “the second intersection with a traffic light” here means the intersection cr2, so that the searched route Rt may be the route as shown in FIG. 4. Therefore, the driver may be confused which intersection to turn at is the turn intersection.